Manufacture of impregnated fiber articles or sheets



Patented Dec. 17, 1935 I UNITED STATES PATENT OFFICE MANUFACTURE OFIMPREGNA'I'ED FIBER- ARTICLES OB SHEETS No Drawing.

8 Claims.

'butthis invention is concerned more especially with webs prepared onmachinery of the paper- 15 making type, such as so-called Fourdrinier orcylinder machines,- from cellulose fibers like preliberated wood pulp.

In accordance with the present invention, we first associate with thefiber articles or sheets so-called regenerated cellulose as animpregnating phase while still preserving, if desired, residual porosityin such articles or sheets. We then associate with such articles orsheets a solid, water-repellent phase in fluxed condition distinct fromand enveloping the regenerated cellulose phase, for instance a fluxed,water-repellent phase of rubber, asphalt, rosin, wax, celluloid, or anyother water-repellent material which can be liquefied and fluxed by heator by organic solvents. The secondary enveloping phase may be animpregnating and/or coating one and impart primarily such qualities aswater-repellency and body or stiffness to the web, if desired. In anyevent, however, the secondary phase is preferably present in dominatingproportion over the primary impregnating phase of regenerated cellulose,which may, in fact, constitute only a small fraction by weight of thesecondary phase. The regenerated cellulose is characterized by itsinertness for all practical purposes toward the liquefied and fiuxedbodies which we use for the articles or sheets. This is true whether thebodies are liquefied and fluxed by heat or by solution in an organicsolvent. Indeed, regenerated cellulose is more or less like cellulosefiber in its quality of inertness.

The principles of the present invention may be availed of in variousconnections. Thus, the regeneratedcellulose phase may serve as avaluable one in fibrous articles or sheets which are to undergoimpregnation with, liquefied and fluxed, water-insoluble bodies. Forexample, when one; uses waterlaidwebs of cellulose fiber 'as thefoundations to be impregnated, it is de:

sirable that such websbe highly porous and thus Application September2-, 1932, Serial No. 631,496

be able to imbibe the liquefied impregnant quick-- ly and uniformly. Formany impregnated foundations, the best kind of waterlaid web is onewhich has substantially the same compactness as deposited from aqueoussuspension and dried. In 5 other words, the web may undergo theapplication of little, if any, outside pressure during its traverse ofboth the wet and dry ends of the papermaking machine on which it isprepared. The fibers of such a web are hence only loosely interfeltedbecause, other thanthe action of surface tension in drawing together thefib'ers during drying, they have been compacted only slightly, if atall. The web is hence bulky, highly porous, and able to imbibe readilylarge quantities of liquid impregnant, for instance a quantity by weighttwice or even more than the weight of the dry web. The raw or waterleafweb is, however, tender or lacking in much tensile strength. Byassociating only a. small amount of regenerated cellulose with such aweb so as to preserve most, I if not substantially all, of its porosity,the web is improved vastly for impregnation with various liquefied andfluxed impregnants. The regenerated-cellulose-containing web has muchless tendency to disintegrate when it is drawn under stress as acontinuous sheet through one or more baths of the fiuxed,water-insoluble impregnants. It can be passed continuously through anorganic solvent solution of rubber, e. g., a rubber-benzol solution, andthen dried without danger of breaking in its journey to produce afinished product having high tear resistance, toughness,waterrepellency, and other leather-simulating qualities.

The increased strength imparted to the web by the regenerated celluloseis not lost when the web is impregnated with heat-liquefied impregnants,e. g., molten asphalt, rosin, waxes, or similar thermoplastic bodies, asthe regenerated cellulose is stable at those temperatures which 40render these bodies sufliciently fluid to enter into and through the webreadily. The web can be impregnated with large quantities of asphalt orother bitumens to produce an impregnated sheet containing upwards of250% asphalt, based on 4 fiber; and thus highly serviceable for roofing,fiooring, or other building purposes on account of its high tearresistance, water repellency, and weathering capacity. The impregnationof the web with molten rosin alone or together, if desired, with moltenasphalt or similar thermoplastic agents followed by cooling of theimpregnated web results in a stiff, resilient sheet eminentlysatisfactory for use in making socalled thermoplastic shoe stiffenerparts, e. g.,

box toe blanks, which are molded in a heatsoftened condition to thedesired shape in the shoe. When the web is to undergo impregnation witha heat-liquefied impregnant, e. g., asphalt, at least a portion of itsfiber content may be asbestos and/or wool and/or other non-cellulosicfiber which is heat-resistant.

Nor is the increased strength imparted to the web by the regeneratedcellulose lost when the web is dipped into baths made up of theheatfusible impregnants mentioned, or of resins (natural or synthetic)nitrocellulose, cellulose acetate, celluloid, or other cellulosederivatives dissolved in suitable organic solvents. In fact, theregenerated cellulose is insoluble in the common organic solvents likealcohol, ether, ethyl acetate, benzol, toluol, carbon tetrachloride,chloroform, or the like. The web may, for example, be impregnated with anitrocellulose, cellulose acetate, or celluloid solution, and thesolvent then evaporated to produce a stiffened, resilient, flexible, andwaterproof sheet suitable for various purposes in the arts. Box toeblanks may be cut from such a sheet and assembled with the shoe uppersin limp, solvent-treated condition and then allowed to set or stiffen inplace in the shoes.

The association of the regenerated cellulose with the web may beaccomplished in various ways, but. we prefer to regenerate the cellulosefrom a cellulose xanthate or viscose solution because of the low cost ofthis cellulose derivative and the comparative ease with which thecellulose may be regenerated therefrom. The viscose solution may beadded to the aqueous fiber suspension from which the web is made, but weprefer to add this solution to the web at any suitable stage of itstravel on the papermaking machine or to the prefabricated web. Theconcentration and the amount of viscose solution added may be adjustedto deposit, say, about 1% regenerated cellulose in the web, based on theweight of fiber, although, if desired, this percentage may be somewhatlower or as high as 3% or even much higher. Ordinarily, however, about1% regenerated cellulose is ample to effect the desired strengthening ofthe web; and this percentage does not detract appreciably from the webabsorbency.

The cellulose may be regenerated in the web by subjecting theviscose-treated web to the action of suitable regenerating chemicalssuch as acid or acid salt solutions and/or to the action of heat. Thus,the drying of the viscose-treated web under heat regenerates thecellulose therein: If desired, the viscose solution used as the initialimpregnant for the web may be treated with such acids as boric oracetic, which can be added to the viscose solution in such amount as toneutralize part of the alkali in the solution without causing a gellingof the solution. The partly neutralized viscose solution may then beapplied as the primary impregnant to the web. The addition of such acidsto a viscose solution promotes the subsequent regeneration of thecellulose therefrom in the web, When the viscose solution is used intreating a prefabricated dried web, it may be applied, as by a sprayingor coating device, to only one face of the web so as to effect only apartial impregnation; or it may be applied in such a way as to produce asubstantially uniformly impregnated web. For instance, the dried,prefabricated web may be passed through a bath of the viscose solution,or the viscose solution may be applied to one face of the web and thenpassed over a suction box, to cause a penetration bleached or insubstantially unbleached condition.

We prefer to use refined wood pulps of an alpha cellulose content ofabout 93% to 96% when we 15 are seeking webs of the highest absorbency,for

in such case we can readily prepare waterlaid webs of a compactness ofabout 30 to 55 when the papermaking machine for fabricating the webs areoperated in such a way as to exert no sub- 20 stantial pressure on thewebs at any stage of their journey on the machine. The foregoing valuesof compactness are obtained by dividing the basis weight in pounds bythe thickness in inches and multiplying by the factor 10 The 25expression basis weight as known in papermaking circles representsweight in pounds of 480 sheets whose dimensions are 24 x 36 inches, thisbeing equivalent to 2880 square feet of sheet materiaL- In other wordsthe compactness value 30 really represents the weight of fiber per unitvolume of sheet material.

In some instances, the fiber article being treated in accordance withour invention may advantageously be a paper made from beaten pulp as 35ordinarily and with which regenerated cellulose has been associated atany suitable stage of papermaking. In fact, such paper maybe associatedadditionally with sizing ingredients, such as glue or rosin. The glue orother sizing agent 40 may be incorporated into the paper at the samestage of paper manufacture as is the regenerated ellulose or at somedifferent stage of paper manufacture. For instance, a mixed glue andviscose solution, a mixed rosin size and viscose solution, 45 or aviscose solution containing both glue and rosin size may be used as theimpregnant for a pre-fabricated, waterleaf web of paper. When glue aswell as regenerated cellulose is incorporated into the paper, suitablemodifying agents may 50 be added to the paper. For instance, glycerinemay be added to the mixed glue and viscose solution to impart pliancy tothe resulting paper. So, too, insolubilizing agents, such asformaldehyde, alum, tannic acid or the like may be added to-the 55 mixedimpregnating solution for the purpose of converting the glue towater-insoluble condiiton when it is dried or set in the paper. Should aglue solution be used independently of the viscose solution as animpregnant, the modifying agents 60 may be added to the glue solutionitself or after the paper has been impregnated with the glue solution orwith both. the glue and viscose solutions. In the event that the papercontaining the regenerated cellulose has been made from 65 well-beatenstock and contains sizing agents, such as glue and/ or rosin, subsequenttreatment of the paper with fluxed, water-repellent bodies inheatliquefied or dissolved condition is accomanied by only surfacepenetration of the paper on account 70 of its density andimpermeability. In other words, the water-repellent body will depositessentially as a continuous coating on the surface of the paper onaccount of the comparatively dense, non-absorptive character acquired bythe 75 paper through the beating of the papermaking stock and/or sizingof its fibers. In thwe instances when it is desired to-produceessentialy a water-repellent paper by coating with organic solventsolutions of cellulose derivatives, such as nitrocellulose, celluloseacetate, or the like, or with molten thermoplastic waterproofing agents,such as waxes, bitumens, or the like, the dense, non-absortive characterof the paper is desirable in that the water-repellent body is confinedlargely to the surface of the paper where it can exercise mosteffectively its water-shedding ability. A paper which containsregenerated cellulose in its interior and is enveloped .by a fluxed, 1solid phase of water-repellent material existing either as a coatingand/or as a partial or complete impregnant for the body of the paper canwithstand most effectively the disintegrating action of water, for evenshould the fluxed phase of water-repellent material be abraded, crackedor otherwise injured, the paper resists rupture on account of the highwet strength imparted thereto by the internal phase of regeneratedcellulose.

We have spoken about the solid phase of waterrepellent material as beingin fluxed condition when it exists primarily in the body of the fibrousarticle and/or on its surface. By fluxed condition, we, mean thecondition of continuity attained in the water-repellent material throughi the action of heat or suitable organic solvents, thereupon.Water-repellent materials do not exercise their maximum potentialwater-repellency when deposited from aqueous suspension or 5 dispersion,as by mere drying. Indeed, unless drying is accomplished under suchelevated temperature conditionsas will fuse the dispersed particles,assuming that' they are fusible, or unless drying is followed bytreatment with suitable or- 40 ganic solvents, the dispersed particleswill not impart maximum water-repellency to the fiber articles intowhich they are incorporated. This is true even of aqueous rubberdispersions, such as latex, whose dispersed particles tend to coalesce45 upon drying. Consequently even when aqueous dispersions of solid,water-repellent materials are used to impregnate a. fiber articlecontaining regenerated cellulose, the dispersed particles are, inaccordance with our invention, fluxed by the 50 action of heat or asuitable organic solvent. It is, however, more direct and economical touse organic solvent solutions of the water-repellent body or to use thebody in fused or molten condition, when it is fusible, in bringing.about the im- .pregnation and/or coating of the fiber articlescontaining the regenerated cellulose so as to realize the articles ofthe present invention.

We do not claim herein specifically the subject matter of ourapplication Serial No. 631,497, filed of even date herewith (now PatentNo. 1,971,274, dated Aug. 21, 1934), wherein we have disclosed andclaimed specifically the use of wax for coating or envelopingsubstantially all of the surfaces of a fibrous article containingregenerated cellu- 65 lose as an impregenating phase.

We claim:

1. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary impregnating phase in the pores andinterstices 70 between the fibers as well as on the fibers and aseparately added secondary impregnating phase of solid, fluxed,water-repellent material enveloping substantially all of the surfaces ofsaid F article, said article being possessed of residual porositysubstantially throughout after the addition of' the primary impregnatingphase but before the addition of the secondary impregnating phase.

2. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary im- .5

' porosity substantially throughout after the addition of the primaryimpregnating phase but before the addition of the secondary impregnatingphase. I

3. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary impregnating phase in the poresandinterstices between the fibers as well as on the fibers and aseparately added secondary phase of solid, sol- 20 vent-fluxed,water-repellent cellulose ester enveloping substantially all of thesurfaces of said article, said article being possessed of residualporosity substantially throughout after the addition of the primaryimpregnating phase but be- 25 fore the addition of the secondaryimpregnating phase.

4. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary impregnating phase in the pores andinterstices between the fibers as well as on the fibers and a separatelyadded secondary impregnating phase of solid, heat-fluxed,water-repellent material enveloping substantially all of the surfaces ofsaid article, said article being possessed of residual porositysubstantially throughout after the addition of the primary impregnatingphase but before the addition of the secondary impregnating phase.

5. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary impregnating phase in the pores andinterstices between the fibers as well as on the fibers and a separatelyadded secondary impregnating phase of fluxed asphalt envelopingsubstantially all of the surfaces of said article, said article beingpossessed of residual porosity substantially throughout after theaddition of the primary impregnating phase but before the addition ofthe secondary impregnating phase.

6. A fibrous article carrying a small percentage of regeneratedcellulose as an added primary impregnating phase in the pores andinterstices between the fibers as well as on the fibers and a.separately added secondary impregnating phase of fluxed rosin envelopingsubstantially all of the surfaces of said article, said article beingpossessed of residual porosity substantially throughout after theaddition of the primary impregnating phase but before the addition ofthe secondary impregnating phase.

7. A fibrous article, at least a portion of whose fiber content isnoncellulosic, carrying a small percentage of regenerated cellulose asan added primary impregnating phase in the pores and 6 intersticesbetween the fibers as well as on the fibers and a separately addedsecondary impregnating phase of solid,fluxed,,water-repellent materialenveloping substantially all of the surfaces of said article, saidarticle being possessed of residual porosity substantially throughoutafter the addition of the primary impregnating phase but before theaddition of the secondary impregnating phase.

8. A fibrous article, at least a portion of whose fiber content isasbestos, carrying a small percentage of regenerated cellulose as anadded primary impregnating phase in the pores and interstiees betweenthe fibers as well as on the fibers 5 and a separately added secondaryimpregnating phase of solid, fluxed, water-repellent material envelopingsubstantially all of the surfaces of said article, said article beingpossessed of residual porosity substantially throughout aft-er theaddition of the primary impregnating phase but before the addition ofthe secondary impregnating phase.

GEORGE A. RICHTER. MILTON O. SCHUR.

